Filter and plasma display device thereof

ABSTRACT

A plasma display device is provided. The plasma display device includes a plasma display panel (PDP) which includes an upper substrate on which a plurality of black matrices are formed; and an external light shielding sheet which is disposed at a front of the PDP and includes a base unit and a plurality of pattern units that are formed on the base unit and that have a lower refractive index than the base unit. A distance between a pair of adjacent black matrices is 4-12 times greater than a distance between a pair of adjacent pattern units. Therefore, it is possible for a plasma display device to effectively realize black images and enhance bright room contrast with the aid of an external light shielding sheet which is disposed at a front of a PDP and which absorbs and shields as much external light incident upon the PDP as possible. Also, it is possible to reduce the probability of occurrence of the moire phenomenon and enhance the luminance of images displayed by a PDP by forming a plurality of pattern units on an external light shielding sheet so that the distance between the pair of adjacent pattern units can fall within a predetermined percentage range of the distance between the pair of adjacent black matrices formed on a PDP, or that the width of the pattern units can fall within a predetermined percentage range of the width of black matrices formed on the PDP.

TECHNICAL FIELD

The present invention relates to a plasma display panel (PDP), and moreparticularly, to a plasma display device in which an external lightshielding sheet is disposed at the front of a PDP in order to shieldexternal light incident upon the PDP so that the bright room contrast ofthe PDP can be enhanced while maintaining the luminance of the PDP.

BACKGROUND ART

In general, plasma display panels (PDPs) display images including textand graphic images by applying a predetermined voltage to a number ofelectrodes installed in a discharge space to cause a gas discharge andthen exciting phosphors with the aid of plasma that is generated as aresult of the gas discharge. PDPs are easy to manufacture aslarge-dimension, light, and thin flat displays. In addition, PDPs canprovide wide vertical and horizontal viewing angles, full colors andhigh luminance.

In the meantime, external light incident upon a PDP may be reflected byan entire surface of the PDP due to white phosphors that are exposed ona lower substrate of the PDP. For this reason, PDPs may mistakenlyrecognize and realize black images as being brighter than they actuallyare, thereby causing contrast degradation.

DISCLOSURE [Technical Problem]

The present invention provides a plasma display device which can preventlight reflection by effectively shielding external light incident upon aplasma display panel (PDP) and which can improve the bright roomcontrast and luminance of a PDP.

[Technical Solution]

According to an aspect of the present invention, there is provided aplasma display device, including a plasma display panel (PDP) whichincludes an upper substrate on which a plurality of black matrices areformed and an external light shielding sheet which is disposed at afront of the PDP and includes a base unit and a plurality of patternunits that are formed on the base unit and that have a lower refractiveindex than the base unit. A distance between a pair of adjacent blackmatrices is 4-12 times greater than a distance between a pair ofadjacent pattern units.

According to another aspect of the preset invention, there is provided aplasma display device, including a PDP which includes an upper substrateon which a plurality of black matrices are formed and an external lightshielding sheet which is disposed at a front of the PDP and includes abase unit and a plurality of pattern units that are formed on the baseunit and that have a lower refractive index than the base unit. Adistance between a pair of adjacent black matrices is 4-9 times greaterthan a distance between a pair of adjacent pattern units.

According to another aspect of the preset invention, there is provided aplasma display device, including a PDP which includes an upper substrateon which a plurality of pairs of electrodes and a plurality of blackmatrices are formed, the black matrices respectively being distant apartfrom the pairs of electrodes and an external light shielding sheet whichis disposed at a front of the PDP and includes a base unit and aplurality of pattern units that are formed on the base unit and thathave a lower refractive index than the base unit. A distance between apair of adjacent black matrices is 7-12 times greater than a distancebetween a pair of adjacent pattern units.

According to another aspect of the preset invention, there is provided aplasma display device, including a PDP which includes an upper substrateon which a plurality of black matrices are formed and an external lightshielding sheet which is disposed at a front of the PDP and includes abase unit and a plurality of pattern units that are formed on the baseunit and that have a lower refractive index than the base unit. A widthof the black matrices is 3-15 times greater than a width of the patternunits.

According to another aspect of the preset invention, there is provided aplasma display device, including a PDP which includes an upper substrateon which a plurality of pairs of electrodes and a plurality of blackmatrices are formed, the black matrices respectively overlapping thepairs of electrodes and an external light shielding sheet which isdisposed at a front of the PDP and includes a base unit and a pluralityof pattern units that are formed on the base unit and that have a lowerrefractive index than the base unit. A width of the black matrices is10-15 times greater than a width of the pattern units.

According to another aspect of the preset invention, there is provided aplasma display device, including a PDP which includes an upper substrateon which a plurality of pairs of electrodes and a plurality of blackmatrices are formed, the black matrices respectively being distant apartfrom the pairs of electrodes and an external light shielding sheet whichis disposed at a front of the PDP and includes a base unit and aplurality of pattern units that are formed on the base unit and thathave a lower refractive index than the base unit. A width of the blackmatrices is 3-7 times greater than a width of the pattern units.

According to another aspect of the preset invention, there is provided afilter that shields external light incident upon a PDP, the filterincluding an external light shielding sheet which is disposed at a frontof the PDP and includes a base unit and a plurality of pattern unitsthat are formed on the base unit and that have a lower refractive indexthan the base unit. A distance between a pair of adjacent black matricesthat are formed on the PDP is 4-12 times greater than a distance betweena pair of adjacent pattern units.

According to another aspect of the preset invention, there is provided afilter that shields external light incident upon a PDP, the filterincluding an external light shielding sheet which is disposed at a frontof the PDP and includes a base unit and a plurality of pattern unitsthat are formed on the base unit and that have a lower refractive indexthan the base unit. A width of black matrices that are formed on the PDPis 3-15 times greater than a width of the pattern units.

ADVANTAGEOUS EFFECTS

The plasma display device according to the present invention includes anexternal light shielding sheet which is disposed at the front of aplasma display panel (PDP) and which absorbs and shields as muchexternal light incident upon the PDP as possible. Thus, the plasmadisplay device according to the present invention can effectivelyrealize black images and enhance bright room contrast. Since thedistance between a pair of adjacent pattern units formed on the externallight shielding sheet is within a predetermined percentage range of thedistance between the pair of adjacent black matrices formed on the PDPor the width of the pattern units formed on the external light shieldingsheet is a predetermined percentage range of the width of black matricesformed on the PDP, it is possible to reduce the probability ofoccurrence of the moire phenomenon and to enhance the luminance ofimages displayed by a PDP.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a plasma display panel according to anembodiment of the present invention;

FIG. 2 is a cross-sectional view of an external light shielding sheetthat is included in a filter according to an embodiment of the presentinvention;

FIG. 3 is a cross-sectional view of an external light shielding sheetaccording to an embodiment of the present invention and explains anexternal light shielding function and a panel light reflection functionperformed by the external light shielding sheet;

FIGS. 4 and 5 are plan views of black matrices that can be formed on aPDP, according to embodiments of the present invention;

FIGS. 6 through 11 are cross-sectional views of various shapes ofpattern units that can be formed in an external light shielding sheet,according to embodiments of the present invention; and

FIG. 12 is a cross-sectional view for explaining the relationshipbetween the thickness of an external light shielding sheet and theheight of pattern units of the external light shielding sheet; and

FIGS. 13 through 16 are cross-sectional views of filters according toembodiments of the present invention, each filter including a pluralityof sheets.

BEST MODE

The present invention will hereinafter be described more fully withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. FIG. 1 is a perspective view of a plasmadisplay panel (PDP) according to an embodiment of the present invention.

Referring to FIG. 1, the PDP includes an upper substrate 10, a pluralityof electrode pairs which are formed on the upper substrate 10 andconsist of a scan electrode 11 and a sustain electrode 12 each, a lowersubstrate 20, and a plurality of address electrodes 22 which are formedon the lower substrate 20.

Each of the electrode pairs includes transparent electrodes 11 a and 12a and bus electrodes 11 b and 12 b. The transparent electrodes 11 a and12 a may be formed of indium-tin-oxide (ITO). The bus electrodes 11 band 12 b may be formed of a metal such as silver (Ag) or chromium (Cr)or may be comprised of a stack of chromium/copper/chromium (Cr/Cu/Cr) ora stack of chromium/aluminium/chromium (Cr/Al/Cr). The bus electrodes 11b and 12 b are respectively formed on the transparent electrodes 11 aand 12 a and reduce a voltage drop caused by the transparent electrodes11 a and 12 a which have a high resistance.

According to an embodiment of the present invention, each of theelectrode pairs may be comprised of the bus electrodes 11 b and 12 bonly. In this case, the manufacturing cost of the PDP can be reduced bynot using the transparent electrodes 11 a and 12 a. The bus electrodes11 b and 12 b may be formed of various materials other than those setforth herein, e.g., a photosensitive material.

Black matrices are formed on the upper substrate 10. The black matricesperform a light shied function by absorbing external light incident uponthe upper substrate 10 so that light reflection can be reduced. Inaddition, the black matrices enhance the purity and contrast of theupper substrate 10.

In detail, the black matrices include a first black matrix 15 whichoverlaps a plurality of barrier ribs 21, a second black matrix 11 cwhich is formed between the transparent electrode 11 a and the buselectrode 11 b of each of the scan electrodes 11, and a second blackmatrix 12 c which is formed between the transparent electrode 12 a andthe bus electrode 12 b. The first black matrix 15 and the second blackmatrices 11 c and 12 c, which can also be referred to as black layers orblack electrode layers, may be formed at the same time and may bephysically connected. Alternatively, the first black matrix 15 and thesecond black matrices 11 c and 12 c may not be formed at the same time,and may not be physically connected.

If the first black matrix 15 and the second black matrices 11 c and 12 care physically connected, the first black matrix 15 and the second blackmatrices 11 c and 12 c may be formed of the same material. On the otherhand, if the first black matrix 15 and the second black matrices 11 cand 12 c are physically separated, the first black matrix 15 and thesecond black matrices 11 c and 12 c may be formed of differentmaterials.

An upper dielectric layer 13 and a passivation layer 14 are deposited onthe upper substrate 10 on which the scan electrodes 11 and the sustainelectrodes 12 are formed in parallel with one other. Charged particlesgenerated as a result of a discharge accumulate in the upper dielectriclayer 13. The upper dielectric layer 13 may protect the electrode pairs.The passivation layer 14 protects the upper dielectric layer 13 fromsputtering of the charged particles and enhances the discharge ofsecondary electrons.

The address electrodes 22 are formed and intersects the scan electrode11 and the sustain electrodes 12. A lower dielectric layer 24 and thebarrier ribs 21 are formed on the lower substrate 20 on which theaddress electrodes 22 are formed.

A phosphor layer 23 is formed on the lower dielectric layer 24 and thebarrier ribs 21. The barrier ribs 21 include a plurality of verticalbarrier ribs 21 a and a plurality of horizontal barrier ribs 21 b thatform a closed-type barrier rib structure. The barrier ribs 21 define aplurality of discharge cells and prevent ultraviolet (UV) rays andvisible rays generated by a discharge from leaking into the dischargecells.

Referring to FIG. 1, a filter 100 is disposed at the front of the PDP.The filter 100 may include an external light shielding sheet, ananti-reflection sheet, a near infrared (NIR) shielding sheet, anelectromagnetic interference (EMI) shielding sheet, a diffusion sheet,and an optical sheet.

When the filter 100 is 10-30 μm distant apart from the PDP, the filter100 can effectively shield external light incident upon the PDP anddischarge light generated by the PDP to the outside of the PDP. In orderto protect the PDP against external pressure, the distance between thefilter 100 and the PDP may be set to 30-120 μm. For shock prevention, anadhesive layer which can absorb shock may be formed between the filter100 and the PDP.

The present invention can be applied to a barrier rib structure otherthan that set forth herein. For example, the present invention can beapplied to a differential barrier rib structure in which the height ofvertical barrier ribs 21 a is different from the height of horizontalbarrier ribs 21 b, a channel-type barrier rib structure in which achannel that can be used as an exhaust passage is formed in at least onevertical or horizontal barrier rib 21 a or 21 b, and a groove-typebarrier rib structure in which a groove is formed in at least onevertical or horizontal barrier rib 21 a or 21 b. In the differentialbarrier rib structure, the height of horizontal barrier ribs 21 b may begreater than the height of vertical barrier ribs 21 a. In thechannel-type barrier rib structure or the groove-type barrier ribstructure, a channel or a groove may be formed in at least onehorizontal barrier rib 21 b.

According to the present embodiment, red (R), green (G), and blue (B)discharge cells are arranged in a straight line. However, the presentinvention is not restricted to this. For example, R, G, and B dischargecells may be arranged as a triangle or a delta. Alternatively, R, G, andB discharge cells may be arranged as a polygon such as a rectangle, apentagon, or a hexagon.

The phosphor layer 23 is excited by UV rays that are generated upon agas discharge. As a result, the phosphor layer 23 generates one of R, G,and B rays. A discharge space is provided between the upper and lowersubstrates 10 and 20 and the barrier ribs 21. A mixture of inert gases,e.g., a mixture of helium (He) and xenon (Xe), a mixture of neon (Ne)and Xe, or a mixture of He, Ne, and Xe is injected into the dischargespace.

FIG. 2 is a cross-section view of an external light shielding sheet thatis included in a filter according to an embodiment of the presentinvention. Referring to FIG. 2, the external light shielding sheetincludes a base unit 200 and a plurality of pattern units 210.

The base unit 200 may be formed of a transparent plastic material, e.g.,a UV-hardened resin-based material, so that light can smoothly transmittherethrough. Alternatively, the base unit 200 may be formed of a rigidmaterial such as glass in order to enhance the protection of an entiresurface of a PDP.

Referring to FIG. 2, the pattern units 210 may be formed as triangles.The pattern units 210 are formed of a darker material than the base unit200. The pattern units 210 may be formed of a black material. Forexample, the pattern units 210 may be formed of a carbon-based materialor black dye may be applied onto the pattern units 210 so thatabsorption of external light by the pattern units 210 can be maximized.

Referring to FIG. 2, a position below the external light shielding sheetwill hereinafter be referred to as a panel side, and a position abovethe external light shielding sheet upon which external light is incidentwill hereinafter be referred to as a user side. Since an external lightsource is generally located above a PDP, external light is highly likelyto be diagonally incident upon a PDP from above. In order to shieldexternal light through light absorption and to enhance the reflection ofpanel light through total reflection of visible light emitted from aPDP, the refractive index of the patter units 210, particularly, therefractive index of at least the slanted surfaces of the pattern units210, may be lower than the refractive index of the base unit 200.

FIG. 3 is a cross-sectional view of an external light shielding sheetaccording to an embodiment of the present invention and explains anexternal light shielding function and a panel light reflection functionperformed by the external light shielding sheet.

As described above, external light which reduces the bright roomcontrast of a PDP is highly likely to be incident upon a PDP from above.Referring to FIG. 3, according to Snell's law, external light that isdiagonally incident upon the external light shielding sheet, asindicated by dotted lines, is refracted into and absorbed by a pluralityof pattern units 310 which have a lower refractive index than a baseunit 300. External light refracted into the pattern units 310 may beabsorbed by light absorption particles in the pattern units 310.

Light that is emitted from a PDP 320 for displaying an image, asindicated by solid lines, is totally reflected from the slanted surfacesof the pattern units 310 to the outside of the external light shieldingsheet, i.e., toward the user side.

As described above, external light is refracted into and absorbed by thepattern units 310 and light emitted from the PDP 320 is totallyreflected by the pattern units 310 because the angle between theexternal light and each of the slanted surfaces of the pattern units 310is greater than the angle between the light emitted from the PDP 320 andeach of the slanted surfaces of the pattern units 310, as illustrated inFIG. 3.

Therefore, the external light shielding sheet according to the presentembodiment can prevent external light incident upon the PDP 320 frombeing reflected toward the user side by absorbing the external light andcan enhance the bright room contrast of an image displayed by the PDP320 by increasing the reflection of light emitted from the PDP 320.

In order to maximize the absorption of external light and the totalreflection of light emitted from the PDP 320 in consideration of theincident angle of external light to the PDP 320, the refractive index ofthe pattern units 310 may be 0.3-1 times higher than the refractiveindex of the base unit 300. In order to maximize the total reflection oflight emitted from the PDP 320 by the slanted surfaces of the patternunits 310, the refractive index of the pattern units 310 may be set tobe 0.3-0.8 times higher than the refractive index of the base unit 300in consideration of a vertical viewing angle of the PDP 320.

FIGS. 4 and 5 are plan views of black matrices 410 and 450,respectively, which can be formed on a PDP according to an embodiment ofthe present invention.

Referring to FIG. 4, the black matrices 410 are formed and overlaprespective corresponding horizontal barrier ribs that are formed on alower substrate 400. Also, the black matrices 410 may overlap respectivecorresponding electrode pairs that are formed on an upper substrate andthat include a scan electrode and a sustain electrode each. As a result,the black matrices 410 can hide the respective electrode pairs.

When the width b of the black matrices 410 is 200-400 μm and thedistance a between a pair of adjacent black matrices 410 is 300-600 μm,an optimum opening ratio for optimizing the luminance of imagesdisplayed by a PDP can be secured, and the efficiency of shielding lightby absorbing external light and by reducing the reflection of theexternal light and the efficiency of enhancing the purity and contrastof an upper substrate can be maximized. Referring to FIG. 5, the blackmatrices 450 are a predetermined distance apart from respectivecorresponding electrode pairs, each electrode pair comprising a scanelectrode 430 and a sustain electrode 440.

The width d of the black matrices 450 is 70-150 μm and the distance cbetween a pair of adjacent black matrices 450 is 500-800 μm, theefficiency of shielding light by absorbing external light and byreducing the reflection of the external light and the efficiency ofenhancing the purity and contrast of an upper substrate can bemaximized.

FIGS. 6 through 11 are cross-sectional views of external light shieldingsheets according to embodiments of the present invention. The externallight shielding sheet illustrated in FIG. 6 includes a base unit 500 anda plurality of pattern units 510.

Referring to FIG. 6, a position below the external light shielding sheetwill hereinafter be referred to as a panel side, and a position abovethe external light shielding sheet upon which external light is incidentwill hereinafter be referred to as a user side. Since an external lightsource is generally located above a PDP, external light is highly likelyto be diagonally incident upon a PDP from above.

In order to shield external light through light absorption and toenhance the reflection of panel light through total reflection ofvisible light emitted from a PDP, the refractive index of the patterunits 510, particularly, the refractive index of at least the slantedsurfaces of the pattern units 510, may be lower than the refractiveindex of the base unit 500.

External light which reduces the bright room contrast of a PDP is highlylikely to be incident upon a PDP from above. Referring to FIG. 6,according to Snell's law, external light that is diagonally incidentupon the external light shielding sheet is refracted into and absorbedby the pattern units 510 which have a lower refractive index than thebase unit 500. External light refracted into the pattern units 510 maybe absorbed by light absorption particles in the pattern units 510.

Light that is emitted from a PDP for displaying an image is totallyreflected from the slanted surfaces of the pattern units 510 to theoutside of the external light shielding sheet, i.e., toward the userside.

As described above, external light is refracted into and absorbed by thepattern units 510 and light emitted from a PDP is totally reflected bythe pattern units 510 because the angle between the external light andeach of the slanted surfaces of the pattern units 510 is greater thanthe angle between the light emitted from the PDP and each of the slantedsurfaces of the pattern units 510, as illustrated in FIG. 6.

Therefore, the external light shielding sheet according to the presentembodiment can prevent external light incident upon a PDP from beingreflected toward the user side by absorbing the external light and canenhance the bright room contrast of an image displayed by the PDP byincreasing the reflection of light emitted from the PDP.

In order to maximize the absorption of external light and the totalreflection of light emitted from a PDP in consideration of the incidentangle of external light to the PDP, the refractive index of the patternunits 510 may be 0.3-1 times higher than the refractive index of thebase unit 500. In order to maximize the total reflection of lightemitted from a PDP by the slanted surfaces of the pattern units 510, therefractive index of the pattern units 510 may be set to be 0.3-0.8 timeshigher than the refractive index of the base unit 500 in considerationof a vertical viewing angle of the PDP.

The base unit 500 may be formed of a transparent plastic material, e.g.,a UV-hardened resin-based material, so that light can smoothly transmittherethrough. Alternatively, the base unit 500 may be formed of a rigidmaterial such as glass in order to enhance the protection of an entiresurface of a PDP.

Referring to FIG. 6, the pattern units 510 may be formed as triangles.The pattern units 510 are formed of a darker material than the base unit500. The pattern units 510 may be formed of a black material. Forexample, the pattern units 510 may be formed of a carbon-based materialor black dye may be applied onto the pattern units 510, therebymaximizing absorption of external light by the pattern units 510.

In order to facilitate the manufacture of light absorption particles andthe insertion of the light absorption particles into the pattern units510 and to maximize the absorption of external light, the lightabsorption particles may be formed to have a size of 1 μm or more. Inorder to effectively absorb external light refracted into the patternunits 510, the pattern units 510 may contain at least 10 weight % oflight absorption particles having a size of 1 μm or more. In this case,the total weight of light absorption particles contained in the patternunits 510 may account for at least 10% of the total weight of thepattern units 510.

When the thickness T of the external light shielding sheet is 20-250 μm,the manufacture of the external light shielding sheet can be facilitatedand the transmissivity of the external light shielding sheet can beoptimized. The thickness T may be set to 100-180 μm in order toeffectively absorb and shield external light refracted into the patternunits 510 and to enhance the durability of the external light shieldingsheet.

Referring to FIG. 6, the pattern units 510 may be formed as triangles,and particularly, as equilateral triangles. The bottom width P1 may be18-35 μm. In this case, light emitted from a PDP can be smoothlydischarged toward the user side. Thus, it is possible to guarantee anoptimum opening ratio and maximize external light shielding efficiency.

The height h of the pattern units 510 is set to 80-170 μm inconsideration of the bottom width P1. Thus, the pattern units 510 canform a gradient that can effectively absorb external light and reflectlight emitted from a PDP. In addition, the pattern units 510 can beprevented from being short-circuited.

In order to achieve a sufficient opening ratio to display images withoptimum luminance through discharge of light emitted from a PDP towardthe user side and to provide an optimum gradient for the pattern units510 for enhancing the external light shielding efficiency and thereflection efficiency of an external light shielding sheet, the distanceD1 between the bottoms of a pair of adjacent pattern units 510 may beset to 40-90 μm, and the distance D2 between the tops of the pair ofadjacent pattern units 510 may be set to 60-130 μm. An optimum openingratio for displaying images can be obtained when the distance D1 is1.1-5 times greater than the bottom width P1. In order to obtain anoptimum opening ratio and to optimize the external light shieldingefficiency and the reflection efficiency of an external light shieldingsheet, the distance D1 may be set to be 1.5-3.5 greater than the bottomwidth P1.

When the height h is 0.89-4.25 times greater than the distance D1,external light that is diagonally incident upon the external lightshielding sheet from above can be prevented from being incident upon aPDP. In order to prevent the pattern units 510 from beingshort-circuited and to optimize the reflection of light emitted from aPDP, the height h may be set to be 1.5-3 times greater than the distanceD1.

When the distance D2 is 1-3.25 times greater than the distance D1, asufficient opening ratio to display images with optimum luminance can beobtained. In order to maximize the total reflection of light emittedfrom a PDP by the slanted surfaces of the pattern units 510, thedistance D2 may be set to be 1.2-2.5 times greater than the distance D1.

Referring to FIG. 7, each of a plurality of pattern units 520 may behorizontally asymmetrical. In other words, a pair of slanted surfaces ofeach of the pattern units 520 may have different areas or may formdifferent angles with the bottom of a corresponding pattern unit 520. Ingeneral, an external light source is located above a PDP. Thus, externallight is highly likely to be incident upon a PDP from above at variousangles within a predetermined range. One of a pair of slanted surfacesof each of the pattern units 510 upon which external light is directlyincident will hereinafter be referred to as an upper slanted surface,and the other slanted surface will hereinafter be referred to as a lowerslanted surface. In order to enhance the absorption of external lightand the reflection of light emitted from a PDP, the upper slantedsurfaces of the pattern units 510 may be less steep than the lowerslanted surfaces of the pattern units 510. That is, the slope of theupper slanted surfaces of the pattern units 510 may be less than theslope of the lower slanted surface of the pattern units 510.

Referring to FIG. 8, a plurality of pattern units 530 may betrapezoidal. In this case, the top width P2 of the pattern units 530 isless than the bottom width P1 of the pattern units 530. The top width P2may be 10 μm or less. The slope of the slanted surfaces of the patternunits 530 can be appropriately determined according to the relationshipbetween the bottom width P1 and the top width P2 so that the absorptionof external light and the reflection of light emitted from a PDP can bemaximized.

Referring to FIGS. 9 through 11, a pair of slanted surfaces of each of aplurality of pattern units 540, 550, or 560 may have a curved profile.Also, the top or bottom surface of each of the pattern units 540, 550,and 560 may have a curved profile.

Referring to FIGS. 6 through 11, each of the pattern units 510, 520,530, 540, 550, or 560 may have curved edges having a predeterminedcurvature. In particular, the pattern units 510, 520, 530, 540, 550, or560 may have outwardly extending, curved lower edges.

FIG. 12 is a cross-sectional view of an external light shielding sheetaccording to an embodiment of the present invention and explains therelationship between the thickness T of the external light shieldingsheet and the height h of pattern units.

Referring to FIG. 12, in order to enhance the durability of an externallight shielding sheet comprising a plurality of pattern units and securethe transmission of visible light emitted from a PDP for displayingimages, the thickness T may be set to 100-180 μm.

When the height h is within the range of 80-170 μm, the manufacture ofan external light shielding sheet can be facilitated, an optimum openingratio can be obtained, and the shielding of external light and thereflection of light emitted from a PDP can be maximized.

The height h can be varied according to the thickness T. In general,external light that considerably affects the bright room contrast of aPDP is highly likely to be incident upon a PDP from above. Therefore, inorder to effectively shield external light, the height h may be within apredetermined percentage range of the thickness T.

Referring to FIG. 12, as the height h increases, the thickness of a baseunit decreases, and thus, dielectric breakdown is more likely to occur.On the other hand, as the height h decreases, more external light islikely to be incident upon a PDP at various angles within apredetermined range, and thus it becomes more difficult for an externallight shielding sheet to properly shield such external light.

Table 1 presents experimental results obtained by testing a plurality ofexternal light shielding sheets having the same thickness T anddifferent pattern unit heights (h) for whether they cause dielectricbreakdown and whether they can shield external light.

TABLE 1 Thickness (T) of Height (h) of Dielectric External LightExternal Light Pattern Units Breakdown Shielding 120 μm 120 μm ∘ ∘ 120μm 115 μm Δ ∘ 120 μm 110 μm x ∘ 120 μm 105 μm x ∘ 120 μm 100 μm x ∘ 120μm 95 μm x ∘ 120 μm 90 μm x ∘ 120 μm 85 μm x Δ 120 μm 80 μm x Δ 120 μm75 μm x Δ 120 μm 70 μm x Δ 120 μm 65 μm x Δ 120 μm 60 μm x Δ 120 μm 55μm x Δ 120 μm 50 μm x x

Referring to Table 1, when the thickness T is 120 μm and the height h isgreater than 115 μm, pattern units in the external light shielding sheetare highly likely to dielectrically break down, thereby increasingdefect rates. When the height h is less than 115 μm, the pattern unitsare less likely to dielectrically break down, thereby reducing defectrates. When the height h is less than 85 μm, the external lightshielding efficiency of the pattern units is likely to decrease. Whenthe height h is less than 60 μm, external light is likely to be directlyincident upon a PDP.

When the thickness T is 1.01-2.25 times greater than the height h, it ispossible to prevent the upper portions of the pattern units fromdielectrically breaking down and to prevent external light from beingincident upon a PDP. In order to prevent dielectric breakdown of thepattern units and infiltration of external light into a PDP, to increasethe reflection of light emitted from a PDP, and to secure optimumviewing angles, the thickness T may be 1.01-1.5 times greater than theheight h.

Table 2 presents experimental results obtained by testing a plurality ofexternal light shielding sheets having different pattern unit bottomwidth-to-bus electrode width ratios for whether they cause the moirephenomenon and whether they can shield external light, when the width ofbus electrodes that are formed on an upper substrate of a PDP is 90 μm.

TABLE 2 Bottom Width of Pattern External light Units/Width of BusElectrodes Moire shielding 0.10 Δ x 0.15 Δ x 0.20 x Δ 0.25 x ∘ 0.30 x ∘0.35 x ∘ 0.40 x ∘ 0.45 Δ ∘ 0.50 Δ ∘ 0.55 ∘ ∘ 0.60 ∘ ∘Referring to Table 2, when the bottom width P1 of pattern units is0.2-0.5 times greater than the bus electrode width, the moire phenomenoncan be prevented and the amount of external light incident upon a PDPcan be reduced. In order to prevent the moire phenomenon, to effectivelyshield external light, and to secure a sufficient opening ratio todischarge light emitted from a PDP, the bottom width P1 may be 0.25-0.4times greater than the bus electrode width.

Table 3 presents experimental results obtained by testing a plurality ofexternal light shielding sheets having different pattern unit bottomwidth-to-vertical barrier rib width ratios for whether they cause themoire phenomenon and whether they can shield external light, when thewidth of vertical barrier ribs that are formed on a lower substrate of aPDP is 50 μm.

TABLE 3 Bottom Width of Pattern Units/Top Width of Vertical ExternalLight Barrier Ribs Moire shielding 0.10 ∘ x 0.15 Δ x 0.20 Δ x 0.25 Δ x0.30 x Δ 0.35 x Δ 0.40 x ∘ 0.45 x ∘ 0.50 x ∘ 0.55 x ∘ 0.60 x ∘ 0.65 x ∘0.70 Δ ∘ 0.75 Δ ∘ 0.80 Δ ∘ 0.85 ∘ ∘ 0.90 ∘ ∘

Referring to Table 3, when the bottom width P1 is 0.3 0.8 times greaterthan the vertical barrier rib width, the moire phenomenon can beprevented and the amount of external light incident upon a PDP can bereduced. In order to prevent the moire phenomenon, to effectively shieldexternal light, and to secure a sufficient opening ratio to dischargelight emitted from a PDP, the bottom width P1 may be 0.4 0.65 timesgreater than the vertical barrier rib width.

FIGS. 13 through 16 are cross-sectional views of filters according toembodiments of the present invention, each filter including a pluralityof sheets. A filter, which is disposed at the front of a PDP, mayinclude an AR/NIR sheet, an EMI shielding sheet 1020, an external lightshielding sheet 1030, and an optical sheet.

Referring to FIGS. 13 and 14, a filter 1000 includes an AR/NIR sheet1010, an EMI shielding sheet 1020, and an external light shielding sheet1030. The AR/NIR sheet 1010 includes a base sheet 1013 which is formedof a transparent plastic material, an AR layer 1011 which is attachedonto an entire surface of the base sheet 1013 and reduces glare bypreventing the reflection of external light incident upon a PDP, and anNIR shielding layer 1012 which is attached onto a rear surface of thebase sheet 1013 and shields NIR rays emitted from a PDP so that signalsprovided by a device such as a remote control which transmits signalsusing infrared rays can be smoothly transmitted.

The EMI shielding sheet 1020 includes a base sheet 1022 which is formedof a transparent plastic material and an EMI shielding layer 1021 whichis attached onto an entire surface of the base sheet 1022 and shieldsEMI generated by a PDP so that the EMI can be prevented from beingreleased externally. The EMI shield layer 1021 may be formed of aconductive material in a mesh form. In order to properly ground the EMIshielding layer 1021, an invalid display zone on the EMI shielding sheet1020 where no images are displayed is covered with a conductivematerial.

An external light source is generally located over the head of a userregardless of an indoor or outdoor environment. The external lightshielding sheet 1030 effectively shields external light so that blackimages can be rendered even blacker by a PDP.

An adhesive layer 1040 is interposed between the AR/NIR sheet 1010, theEMI shielding sheet 1020, and the external light shielding sheet 1030 sothat the filter 1000 including the AR/NIR sheet 1010, the EMI shieldingsheet 1020, and the external light shielding sheet 1030 can be firmlyattached onto a PDP. In order to facilitate the manufacture of thefilter 1000, the base sheets 1013 and 1022 may be formed of the samematerial.

Referring to FIG. 13, the AR/NIR sheet 1010, the EMI shielding sheet1020, and the external light shielding sheet 1030 are sequentiallydeposited. Alternatively, the AR/NIR sheet 1010, the external lightshielding sheet 1030, and the EMI shielding sheet 1020 may besequentially deposited, as illustrated in FIG. 13. The order in whichthe AR/NIR sheet 1010, the EMI shielding sheet 1020, and the externallight shielding sheet 1030 are deposited is not restricted to those setforth herein. At least one of the AR/NIR sheet 1010, the EMI shieldingsheet 1020, and the external light shielding sheet 1030 may not beformed.

Referring to FIGS. 15 and 16, a filter 1100, which is disposed at thefront of a PDP, includes an AR/NIR sheet 1110, an EMI shielding sheet1130, an external light shielding sheet 1140, and an optical sheet 1120.The AR/NIR sheet 1110, the EMI shielding sheet 1130, and the externallight shielding sheet 1140 are the same as their respective counterpartsillustrated in FIGS. 12 and 13. The optical sheet 1120 enhances thecolor temperature and luminance properties of light incident upon a PDPfrom above. The optical sheet 1120 includes a base sheet 1122 which isformed of a transparent plastic material, and an optical sheet layer1121 which is formed of a dye and an adhesive on a front or rear surfaceof the base sheet 1122.

At least one of the base sheets 1013 and 1022 illustrated in FIGS. 12and 13 and at least one of a base sheet 1113, a base sheet 1112, and thebase sheet 1122 illustrated in FIGS. 15 and 16 may not be formed. One ofthe base sheets 1013 and 1022 illustrated in FIGS. 13 and 14 and one ofthe base sheets 1113, 1112, and 1122 illustrated in FIGS. 15 and 16 maybe formed of such a rigid material as glass, instead of being formed ofa plastic material, so that the protection of a PDP can be enhanced.Whichever of the base sheets 1013 and 1022 illustrated in FIGS. 13 and14 and the base sheets 1113, 1112, and 1122 illustrated in FIGS. 15 and16 is formed of glass may be a predetermined distance apart from a PDP.

A filter according to an embodiment of the present invention may alsoinclude a diffusion sheet. The diffusion sheet can diffuse lightincident upon a PDP so that the brightness of the PDP can be uniformlymaintained. In addition, the diffusion sheet can widen vertical andhorizontal viewing angles of a display screen by uniformly diffusinglight emitted from a PDP. Moreover, the diffusion sheet can hidepatterns formed on an external light shielding sheet. Furthermore, thediffusion sheet can uniformly enhance the front luminance of a PDPthrough collection of light in a direction corresponding to a verticalviewing angle, and can enhance the antistatic property of a PDP.

The diffusion sheet may be comprised of a transparent or reflectivediffusion film. In general, the diffusion sheet may be comprised of apolymer base sheet containing small glass particles. The diffusion sheetmay also be comprised of a polymethyl-methacrylate (PMMA) base sheet. Inthis case, the diffusion sheet is thick and highly heat-resistant andcan thus be applied to large-scale display devices which generate aconsiderable amount of heat.

INDUSTRIAL APPLICABILITY

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A plasma display device, comprising: a plasma display panel (PDP)which includes an upper substrate on which a plurality of black matricesare formed; and an external light shielding sheet which is disposed at afront of the PDP and includes a base unit and a plurality of patternunits that are formed on the base unit and that have a lower refractiveindex than the base unit, wherein a distance between a pair of adjacentblack matrices is 4 12 times greater than a distance between a pair ofadjacent pattern units.
 2. The plasma display device of claim 1, whereinthe refractive index of the pattern units is 0.3-1 times higher than therefractive index of the base unit.
 3. The plasma display device of claim1, wherein a height of the pattern units is greater than a height of theblack matrices.
 4. The plasma display device of claim 1, wherein a widthof the pattern units is less than a width of the black matrices.
 5. Theplasma display device of claim 1, wherein the distance between the pairof adjacent black matrices is 300-800 μm.
 6. The plasma display deviceof claim 1, wherein a distance between bottoms of the pair of adjacentpattern units is 40-90 μm.
 7. The plasma display device of claim 1,wherein a thickness of the external light shielding sheet is 1.01-2.25times greater than a height of the pattern units.
 8. The plasma displaydevice of claim 1, wherein the distance between the pair of adjacentpattern units is 2.5-5 times greater than a bottom width of the patternunits.
 9. The plasma display device of claim 1, wherein a height of thepattern units is 1.1-5 times greater than the distance between the pairof adjacent pattern units.
 10. The plasma display device of claim 1,further comprising an anti-reflection (AR) layer which preventsreflection of external light; a near infrared (NIR) shielding layerwhich shields NIR rays emitted from the PDP; and an electromagneticinterference (EMI) shielding layer which shields EMI.
 11. A plasmadisplay device, comprising: a PDP which includes an upper substrate onwhich a plurality of black matrices are formed; and an external lightshielding sheet which is disposed at a front of the PDP and includes abase unit and a plurality of pattern units that are formed on the baseunit and that have a lower refractive index than the base unit, whereina distance between a pair of adjacent black matrices is 4-9 timesgreater than a distance between a pair of adjacent pattern units. 12.The plasma display device of claim 11, wherein the distance between thepair of adjacent black matrices is 300-600 μm.
 13. A plasma displaydevice, comprising: a PDP which includes an upper substrate on which aplurality of pairs of electrodes and a plurality of black matrices areformed, the black matrices respectively being distant apart from thepairs of electrodes; and an external light shielding sheet which isdisposed at a front of the PDP and includes a base unit and a pluralityof pattern units that are formed on the base unit and that have a lowerrefractive index than the base unit, wherein a distance between a pairof adjacent black matrices is 7-12 times greater than a distance betweena pair of adjacent pattern units.
 14. The plasma display device of claim13, wherein the distance between the pair of adjacent black matrices is300-800 μm.
 15. A plasma display device, comprising: a PDP whichincludes an upper substrate on which a plurality of black matrices areformed; and an external light shielding sheet which is disposed at afront of the PDP and includes a base unit and a plurality of patternunits that are formed on the base unit and that have a lower refractiveindex than the base unit, wherein a width of the black matrices is 3-15times greater than a width of the pattern units.
 16. The plasma displaydevice of claim 15, wherein the refractive index of the pattern units is0.3-1 times higher than the refractive index of the base unit.
 17. Theplasma display device of claim 15, wherein the width of the blackmatrices is 70-400 μm.
 18. The plasma display device of claim 15,wherein the width of the pattern units is 18-35 μm.
 19. The plasmadisplay device of claim 15, wherein a thickness of the external lightshielding sheet is 1.01-2.25 times greater than a height of the patternunits.
 20. The plasma display device of claim 15, wherein the distancebetween the pair of adjacent pattern units is 1.1-5 times greater than abottom width of the pattern units.
 21. The plasma display device ofclaim 15, wherein a height of the pattern units is 0.89-4.25 timesgreater than the distance between the pair of adjacent pattern units.22. The plasma display device of claim 15, further comprising: an ARlayer which prevents reflection of external light; an NIR shieldinglayer which shields NIR rays emitted from the PDP; and an EMI shieldinglayer which shields EMI.
 23. A plasma display device, comprising: a PDPwhich includes an upper substrate on which a plurality of pairs ofelectrodes and a plurality of black matrices are formed, the blackmatrices respectively overlapping the pairs of electrodes; and anexternal light shielding sheet which is disposed at a front of the PDPand includes a base unit and a plurality of pattern units that areformed on the base unit and that have a lower refractive index than thebase unit, wherein a width of the black matrices is 10-15 times greaterthan a width of the pattern units.
 24. The plasma display device ofclaim 23, wherein the width of the black matrices is 200-400 μm.
 25. Aplasma display device, comprising: a PDP which includes an uppersubstrate on which a plurality of pairs of electrodes and a plurality ofblack matrices are formed, the black matrices respectively being distantapart from the pairs of electrodes; and an external light shieldingsheet which is disposed at a front of the PDP and includes a base unitand a plurality of pattern units that are formed on the base unit andthat have a lower refractive index than the base unit, wherein a widthof the black matrices is 3-7 times greater than a width of the patternunits.
 26. The plasma display device of claim 25, wherein the width ofthe black matrices is 200-400 μm.
 27. A filter that shields externallight incident upon a PDP, the filter comprising: an external lightshielding sheet which is disposed at a front of the PDP and includes abase unit and a plurality of pattern units that are formed on the baseunit and that have a lower refractive index than the base unit, whereina distance between a pair of adjacent black matrices that are formed onthe PDP is 4-12 times greater than a distance between a pair of adjacentpattern units.
 28. The filter of claim 27, wherein the refractive indexof the pattern units is 0.3-1 times higher than the refractive index ofthe base unit.
 29. The filter of claim 27, wherein the distance betweenthe pair of adjacent black matrices is 300-800 μm.
 30. The filter ofclaim 27, wherein a distance between bottoms of the pair of adjacentpattern units is 40-90 μm.
 31. A filter that shields external lightincident upon a PDP, the filter comprising: an external light shieldingsheet which is disposed at a front of the PDP and includes a base unitand a plurality of pattern units that are formed on the base unit andthat have a lower refractive index than the base unit, wherein a widthof black matrices that are formed on the PDP is 3-15 times greater thana width of the pattern units.
 32. The filter of claim 31, wherein therefractive index of the pattern units is 0.3-1 times higher than therefractive index of the base unit.
 33. The filter of claim 31, whereinthe width of the black matrices is 70-400 μm.
 34. The filter of claim31, wherein the width of the pattern units is 18-35 μm.